1. Field of the Invention
The present invention relates to formation of a dielectric thin film to be used for various electric elements such as an insulated-gate type field-effect transistor and a thin film capacitor having a laminated structure of metal-insulator-metal. More particularly, it relates to a material for use in chemical vapor deposition (CVD), a method of forming a high dielectric constant thin film by CVD and a CVD apparatus for deposition of the high dielectric constant thin film.
2. Description of the Background Art
With advancement in miniaturization of semiconductor devices, materials employed as dielectric thin films to be used for various electric elements in semiconductor devices are being changed. Recent years, requests have been made for improved storage charge density, for example. Accordingly, the use of a dielectric material having a higher dielectric constant is now under study, instead of a silicon oxide film which has conventionally been employed as a dielectric thin film.
For instance, study is being made as to employment of a high dielectric thin film in a silicon CMOS (Complementary Metal Oxide Semiconductor) logic device instead of a conventional silicon oxynitride film. This is because a next-generation MOSFET is required to ensure high mutual conductance. This is discussed by Wen-Jie Qi et al. in xe2x80x9cPerformance of MOSFETs with ultra thin ZrO2 and Zr-silicate gate dielectricsxe2x80x9d, 2000 Symposium on VLSI Technology Digest of Technical Papers (2000) (pp. 40-41), for example.
For the purpose of miniaturization of a high frequency device represented by a GaAs MMIC (Microwave Monolithic IC), miniaturization and integration of an electric element such as a bypass capacitor is now under study. In this study, it is considered to use a thin film capacitor in which a high dielectric constant thin film is employed instead of a conventional silicon nitride film or the like. This is discussed by S. Nagata et al. in xe2x80x9cA GaAs MMIC Chip-Set for Mobile Communications Using On-Chip Ferroelectric Capacitorsxe2x80x9d, 1993 IEEE International Solid-State Circuits Conference (1993) (p. 285), for example.
In order to improve storage charge density of a memory cell in a memory device such as DRAM (Dynamic Random Access Memory), the use of a memory cell capacitor using a high dielectric constant thin film is now under study, instead of a stacked structure of a conventional silicon oxide film and a conventional silicon nitride film.
As a high dielectric constant thin film suitable for these applications, attention is now being directed particularly to a dielectric film including a silicate compound for its high chemical stability. The aforementioned document by Wen-Jie Qi et al., for example, shows that, in the case where a ZrSiO4 film as a kind of a silicate compound is directly formed on a silicon substrate, heat treatment at about 700xc2x0 C. does not cause significant mutual diffusion between the silicon substrate and the ZrSiO4 film. The document also ascertains the operation of a MOSFET in which an ultra thin ZrSiO4 film is used.
As has been described, a silicate compound is useful for a high dielectric constant film used for various electric elements integrated in a semiconductor device. Among methods of forming such a silicate compound, a sputtering method, a method utilizing heat reaction between ZrO2 and Si and the like are in the mainstream under present circumstances.
In an application of a silicate compound to the actual manufacture of LSI, however, it is desirable to form a high dielectric constant film by CVD in view of smoothness and coverage of a step difference in a finished film.
Nevertheless, materials suitable for achieving film deposition of good quality or combination of such materials in forming a high dielectric constant film including a silicate compound have not been clarified. Further, it has not been clarified what treatment should be given to films deposited by CVD to obtain a high dielectric constant film of good quality.
Particularly, in film formation using a plurality of materials, reaction between the materials often causes generation of dust in the vapor phase, adhesion of deposits to a supply conduit and the like. Therefore, there arise problems such as that the supply of materials becomes unstable, resulting in frequent occurrence of variations in the deposition speed each time of film formation. There are no findings at the moment that can contribute to solution of such instability in film formation of a silicate compound which is a high dielectric constant film.
An object of the present invention is to provide a liquid material for CVD, a method of forming a film by CVD and a CVD apparatus, capable of achieving film formation of a silicate compound of good quality.
An aspect of the present invention is directed to a method of forming a film using chemical vapor deposition, wherein a liquid material for chemical vapor deposition including an organometallic compound, a siloxane compound and an organic solvent for dissolving the organometallic compound and the siloxane compound is vaporized to form one of a film and a precursor film.
The method allows stable deposition of a good quality film in film formation of a silicate compound using CVD. Further, film formation using the liquid material is suitable for the manufacture in light of the ease of material supply.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.